The damaged artwork, with the spray paint barely dry, was rushed down the hall to the museum's conservation lab, where chief conservator Brad Epley quickly began its repair.

The 1929 painting, one of nine by Picasso owned by the Menil, has "an excellent prognosis," Muse said.

The vandal, who has not been identified officially, stenciled a small image of a bullfighter killing a bull and the word "Conquista" on the painting. He fled and wasn't caught.

Houston Police spokesman Victor Senties said the vandalism was being investigated as a criminal mischief case. Anyone who witnessed the attack or has information is asked to call 713-308-0900.

KPRC (Channel 2) interviewed a man who said he captured the vandalism on his phone camera. The witness told Channel 2 the man identified himself as an up-and-coming Mexican-American artist looking to honor Picasso's work.

John and Dominique de Menil acquired "Woman in a Red Armchair" in 1956. It has been displayed often since the Menil Collection opened in 1987 and has been loaned to other museums, including the Museum of Modern Art in New York.

The Menil also owns 14 drawings, a terra-cotta sculpture and more than 100 prints by Picasso.

Muse said the incident brought to mind an act in 1974, when artist Tony Shafrazi, who later became a gallery owner, defaced Picasso's masterpiece "Guernica" at the Museum of Modern Art.